Foam-suppressing detergent compo



Get. 10, 1944. E, HILL, 2,359,913"

FOAM-SUPPRESSING DETERGENT COMPOSITION FOR BEVERAGE CONTAINERS FiledJune 20, 1941 FALLING SOLUTION FALLING SOLUTION FOA m I I r 7 I 2; I Y Ia I 20 r z I 0:

DJ 0.2 0.3 O.i 0.5 0.6 0.7 0.8 0.9 L0

GLUE CONCENTRATION,

' INVENTOR.

EUGENE F. HILL ATTORNEYS Patented Oct. 10, .1

FOAM-SUPPRESSING DETERGENT COMPO- SITION FOR BEVERAGE CONTAINERS ofMichigan Application June 20, 1941, Serial No. 398,939

11 Claims. (Cl. 252-135) The present invention has to do with theproblem of controlling the foaming or foam generation in detergentwashing solutions which are employed in the hydraulic type of beveragecontainer washing machines. The opportunity for agitation and airentrainment is very pronounced in the operation of washing machines ofthis type. Heretofore, the foam generated in the solution-receiving tankhas often been so great as tobuild up and flow over the edge of thetank, thus causing a substantial loss in the detergent. To maintainadequate operation of the washing machine, it has been found necessaryto replace this foam over-flow loss from time to time, thus increasingthe expense for the material and labor required, aside from furtherlosses resulting from the diminished efliciency of the washingoperation. a

It is a general object and nature of my present invention to providemeans for preventing such a foam generation loss. This I accomplish byintroducing a foam control reagent to the washing solution, which sochanges the characterand the like, consist primarily of a water solutionof an alkali metal hydroxide such as sodium or potassium hydroxide.Sodium hydroxide, of course, is the most common of the two and isemployed in this country almost to the exclusion of potassium hydroxide.I have discovered that the addition of relatively small quantities ofalkali metal oxide-silica compounds and of the sulphate salts of suchalkali metals has the effect of promptly rendering unstable thegenerated foam.

Furthermore, I have discovered that the presence of certain organicmaterials in the beverage container washing machine solutions haveheretofore had the resultanteifect of increasing foam generation andstability. These organic materials find their way into the washingmachine solutions as residual matter from the beverage containers. Thus,alkali metal salts of short chain fatty acids, such as predominate inmilk, will increase the foam-generating properties of the washingsolution. Likewise proteinaceous material, such as glue and casein, andcarbohydrates. such as starch and dextrin, usually derived from thelabel glue or adhesive of the containers, increase the foam-generatingability of the washing solution. I, therefore, characterize these alkalimetal salts of short chain fatty acids, proteins and carbohydrates as"foaming agents," as distinguished from the anti-foaming reagent of mypresent invention.

In general, an increase in foam generation and stability results fromincreased amounts of such foaming agent material present in the washingsolution. The product of my present invention, however, possesses thequite unexpected property of producing just the opposite result, namely,a decrease in the foam stability with increasing amounts of such foamingagent content in the solution. This latter result is of particularadvantage in that it permitsthe operator of the washing machine toderive the full benefit and value of the detergent properties of thesolution, and without the necessity of discarding a given batchofsolution whenever such organic foaming agent content therein becomestoo high, which heretofore has occurred before the alkaline content ofthe solution has become spent. My invention thus renders it possible toderive the entire benefit of the alkaline properties of the detergentmaterial.

Another object and advantage of my invention is that it is applicable towashing solutions subjected to a wide range of temperature conditions.Anti-foaming agents which have previously been known and used, have beenfound subject to the disadvantage that they are operable only in certainprescribed temperature ranges. Inasmuch as my invention overcomes thislatter disadvantage, it renders possible a flexibility of use throughoutvarying temperatures, which has been highly desired by those working inthe art.

Additional objects and advantages of the invention shall become apparentas the following description proceeds.

To the accomplishment of the foregoing and related ends, said inventionthen consists of the steps hereinafter fully described and particularlypointed out in the claims.

The annexed drawing and the following description set forth in detailone approved method of carrying out the invention, such disclosedmethod, however, constituting but oneof various ways in which theprinciple of the'inven'tionmay be used.

In said annexed drawing:

Fig. 1 is more or less a diagrammatic representation showing thecharacteristics of the foam generated in a washing solution to which theprinciple of my invention has been applied; Fig. 2 is a view similar toFig. 1, but showing the characteristics of the foam heretofore generatedin washing solutions and without utilizing the foam control of myinvention; and Fig. 3 is a chart showing the typical relationship of theglue or protein content to foam generation of prior art alkalinedetergent solutions and of a detergent solution containing the additionreagent of my instant invention.

The hydraulic type of beverage container or bottle washing machine hasbeen rather extensively adopted. This type of bottle washing machineconsists essentially of a washing solutionreceiving tank from which thesolution is circulated by means of a hydraulic pressure pump andexpelled under considerable pressure through a jet into and about thebottles, and a conveying mechanism or traveling rack for bringing thebottles intermittently into position with respect to such Jets. Thewashing solution is then allowed to fall by gravity back into thesolutionreceiving tank. The forcible spraying of the solution, itsimpacting action upon the bottles, its falling back through space intothe tank,-and the possibility of leaks in the pump circulatory system,all contribute to the extreme amount of agitation which is imposed uponthe solution, as well as affording ample opportunity for entrainment ofair. Thus, the foam generating conditions in such a machine are indeedexcellent, and as this foam is deposited upon the surface of thesolution in the solution-receiving tank, it has an opportunity ofbuilding up to a substantial height so that it ultimately over-flows thetop of the tank and becomes lost in the drainage system of the machine.

The cause of foam formation is not definitely known. Pure liquids do notfoam; whereas, solutions or suspensions of lyophyllic colloids, such asglues, dextrins and many soaps possess this property in marked degree.This much is known, however, that any substance present in a solutionwhich will cause a change in the surface tension thereof, whether suchchange be an increase or a decrease, will facilitate the formation andstabilization of a foam. See Glasstone: "Textbook of Physical Chemistry"(1940-pp. 1226-27); Perry: Chemical Engineers Handbook" (1934- p. 940).Foam control has heretofore been attempted by the addition of oils andvarious organic compounds such as fatty acids and esters. But all suchaddition agents have been found to be unsatisfactory, Primarily becausethey failed either to maintain foam-control for a suflicient period oftime or because they proved ineflectlve within the temperature rangesencountered in the operation of bottle washing machines.

I have examined a large number of substances and made many formulationsof chemical compounds. As a result, I have discovered that the presenceof the alkali metal silicates and the sulphate, along with the causticalkali, produces the desired results of decreasing the stability andbuilding power of the foam generated in the washing solution, as well asrapidly dissipating such foam as is generated. Such alkali metalsilicates have the general formula (in the case of sodium, as the alkalimetal) of XNazQYSiO: where X represents a value of 1 and Y representsany value above and including 1. Particular examples of such compoundsare: sodium orthosilicate, sodium metasilieate. sodium sesquisllicateand waterglass. The silicates and the sulphate salts are present in thedetergent mixture in a minor amount with respect to the caustic present.Caustic alkali in my detergent mixture 7 is present in the amount of orgreater, the alkali metal silicates from 3 to 11% and the sulphatepresent in the amount of approximately 2-896. Thus, I have foundsuitable formulas for the detergent composition to be as follows:

Sodium sesquisilicate (3NazO.2SiO211HzO) 10.9

Sodium sulfa 4.0

Formula 4 Percent by weight Sodium hydroxide 92.6

Anhydrous waterglass (1Na2O.3.22SiO-2) 3.4

Sodium sulfate 4.0

Formula 5 Percent by weight Sodium hydroxide 93.4

Sodium sulfate 4.0

Formulas 1, 2, 3, and 4 can be made by mixing together the separatecomponents. Formulas 1, 2, 3, 4, and 5 can be made by fusing togetherthe separate components, viz., sodium hydroxide, silica or sodiumsilicate and sodium sulfate, and finishing the material in any of avariety of physical forms, such as flaking or granulating. In Formula 5,of course, on heating or fusion; the silica component reacts with aportion of the sodium hydroxide to form a sodium silicate. Formulas 1,2, 3, and 4 can be used by adding the separate components in the givenratios to water to make a solution of the desired strength. Formulas 1,2, 3, and 4 can be used by adding sodium sulfate and the respectivealkali metal silicates listed to a caustic solution in such amounts asto give the same sodium hydroxide, S10: and sulfate ratios as given inFormulas l, 2, 3, and 4, respectively. Each of the above compositionformulas are dissolved in water to make solutions in the concentrationrange of .25% to 10% by weight of the composition.

As such a solution is heated, subjected to hydraulic pressure, forciblyexpelled through the bottle washing Jets and then permitted to fall bygravity into the solution tank, it will form a body of foam in thelatter substantially of the characteristics as shown in Fig. 1. Thus, inFig. 1, it will be noted that the foam has built up rather rapidlyin thecentral portion, or in that zone where the falling solution comes incontact with the main body of the solution. However, the height of thefoam is lowest at its outermost edges, showing that the initiallygenerated foam is quite unstable and that there is a rapid dissipation.I,

The foam contour and characteristics of Fig. 1

is to be compared with those represented in Fig. 2 which shows the typeof foam that is formed by an ordinary alkalinewashing solution, viz.,one in which the dissolved detergent consists of about 90% caustic sodaand sodium carbonate.

In Fig. 2, it will be seen that the initial foam formation at thecentral portion is relatively slow, but, on the other hand, is of astable character and hence, builds up to the maximum height at the outeredges of the body of the solution or of thesolution-receiving tank.

The foam-dissipating detergent composition of my invention has also beenfound to be effective over the relatively wide range of temperaturesencountered in commercial bottle washing machines. Such temperaturesvary from 115 F. to 175 F. I have ascertained that the generation offoam in detergent bottle washing solutions in which the foam-dissipatingcomposition of my invention is not present varies directly in proportionto the temperature. Various organic foam-retarding reagents, which haveheretofore been known, such as kerosene oil, tributyl phosphate, citrateand sulphonated castor oil and the like, are effective only for alimited period of time and below a given temperature. Thus, after oneday of operation, it has been found that such previously used organicfoam-retarding agents completely lost their retarding action and thefoam generation in the washing solution returned to its originalcharacteristics, Just as if no reagent had been added.

On the other hand, the foam control addition reagent of my inventionmaintains its foam depressing and dissipating action for extendedperiods of time and in the relatively higher temperature ranges. Thus,in actual operation on a commercial milk bottle washing machine, a 0.5%concentration solution of the above composition Formula 1 was used for aperiod of 4 weeks and without causing foaming over in the washingsolotion-receiving tank. In the same machine, and under similarconditions, a detergent composition of 90% sodium hydroxide and 10%sodium carbonate, produced foaming over at the end of two days ofoperation. In the actual operation of a soft drink bottle washingmachine where the protein or glue content becomes relatively high due tothe presence of glue from the bottle labels, it was found that the foamcontrol detergent composition of my invention, employed in a 4%concentration solution, could be operated successfully and withoutfoaming over for an indefinite period. In fact, this latter result isattributable to the unusual foam control property of my detergentcomposition of becoming increasingly effective as the glue or proteincontent of the solution-increases.

This last-mentioned novel property of my foam control composition isclearly illustrated by reference to Fig. 3. In this latter figure, thereare shown curves for alkaline detergent bottle washing solutions withand without my foam controlling addition reagent and showing therelationship or glue concentration in the solution to the foam heightinitialb generated, and after a period of five minutes standing. Fig. 3thus illustrates the novel foam-depressing and foam-dissipatingproperties of my invention.

The readings for the vertical ordinates in Fig. 3, viz., foam height,have been obtained from a comparatively simple but quite reliable testmethod. This test method consists in making up a 100 cubic centimetersample of the washing solution, with one or more of the previouslymentioned foaming agents present, heating it to the desired temperatureand then placing in a 250 cc. shaking graduate. The graduate is thengrasped at both ends in each hand and shaken 75 times during a period ofabout 40 to 60 seconds. The graduate is held at an angle of about fromthe horizontal during shaking, with the bottom end of the graduateuppermost. Immediately after shaking, a reading is taken of the heightof the foam in the graduate. Five minutes later, a second reading of thefoam height in the graduate is taken. Thus, a reliable test measurementof the initial foam generating properties, as well as the foamdissipating properties of the solution, are obtained. The results ofthis test method have been substantiated by actual operation in thefield, viz., by operation in commercial hydraulic type bottle washingvmachines.

In the case of Fig. 3, 4% concentration solutions in distilled water, ofthe respective detergent composition, heated to a temperature of 150 F.and with the varying percentages of glue content. were subjected to theabove-outlined test method. The solid curves I and 3 represent theresults obtained with an alkaline detergent in which no foam-depressingor foam-dissipating reagent was present. The dotted line curves 2 and drepresent the results of a detergent comand as the glue content risesabove .15%, thecurve changes in slope and direction, thus illustratingthe increased foam-dissipating property of my foam control compositionwith increased glue or protein content. By comparing curves 2 and d, itwillimmediately be appreciated that the foam-dissipating properties ofthe addition agent of my invention are just the opposite of those of asolution in which such agent is not present.

As hereinbefore indicated, the cause of foam generation is quite obscureand not definitely known, hence, I am unable to ascribe any scientifictheory or principle upon which my invention is founded. It is possiblethat the silicates and sulphate salts'of the alkali metal form achemical compound which has an effect upon the surface tension of thesolution tending to impart to it the non-foaming properties of a pureliquid, thus accounting for the instability of the foam that isproduced.

Other modes of applying the principle of my invention may be employedinstead of the one explained, change being made as regards the methodherein disclosed, provided the step or steps stated by any of thefollowing claims or the equivalent of such stated step or steps beemployed. v

For the purpose of conciseness the letters X and Y in the claims will beunderstood to denote the same values as enunciated in the specificationproper.

I, therefore, particularly point out and distinctly claim as myinvention:

1. The method of washing beverage containers and the like in whichresidual material from the group consisting of alkali metal salts ofshort chain fatty acids, proteins and carbohydrates are present asfoaming agents comprising the-steps of adding a detergent'in an amountforming 0.25 to of the weight of the solution to a quantity of water,said detergent comprising at least 85% by weight of sodium hydroxide, 3to 11% by weight of a water-soluble sodium silicate compound asrepresented by the formula and 2 to 6% by weight of sodium sulfate,heating the resultant solution, withdrawing a portion of said solutionunder hydraulic pressure, forcibly ejecting it into contact with saidcontainers and returning it by gravity fall to the main body of thesolution, whereby foam is generated in the latter but rapidly dissipatedbefore reaching an excessive height and then repeating such withdrawaland return of a portion of said solution.

2. The method of washing beverage containers and the like in whichresidual material from the group consisting of alkali metal salts ofshort chain fatty acids, proteins and carbohydrates are present asfoaming agents, comprising the steps of adding a detergent in an amountforming 0.25 to 10% of the weight of the solution to a quantity ofwater, said detergent comprising at least 85% by weight sodiumhydroxide, 3 to 11% by weight of a water-soluble sodium silicatecompound as represented by the formula XNR2O.Y.S1O2 and 2 to 6% byweight of sodium sulfate, heating the resultant solution, withdrawing aportion of said solution under hydraulic pressure, forcibly ejecting itinto contact with said containers and returning it by gravity fall tothe main body of said solution, whereby foam is generated in the latterbut rapidly dissipated a,sso,a1s

tion of the detergent composition comprising at least 85% by weightsodium hydroxide, 3 to 11% by weight of a water soluble sodium silicate,as

represented by the formula XNmQYSiOz and, 2-6% by weight of sodiumsulfate, the total weight of these three last mentioned componentsrepresenting 0.25% to 1o% of the weight of the aqueous solution, saidsolution having incorporated therein entrained gases causing generationof foam which is rapidly dissipated because of this detergent.

5. A foam-suppressing detergent for washing beverage containers and thelike comprising an alkali metal hydroxide in the amount of at least 85%by weight, 3 to 11% of water-soluble alkali metal oxide-silica compoundof the formula XMezQYSiOz (Me representing a member of the groupconsisting of Na and/K) and 2 to 6% of an alkali metal sulfate.

8. A foam-suppressing detergent for washing beverage containers and thelike comprising sodium hydroxide in the amount of at least 85% byweight, 3 to 11%,by weight of a water-soluble alkali metal oxide-silicacompound of the formula XMezQYSiO: (Me representing a, member of thegroup'consisting of Na and K) and 2 to 0% of an alkali metal sulfate.

7. A foam-dissipating solution for washing beverage containers and thelike containing mostly water, from a mere trace up to 1% proteinaceousmaterial, a detergent comprising at least 85% sodium hydroxide, 3-11% ofwater-soluble alkali metal silicates as represented by the formulaXMezQYSiO: (Me representing a member'of the group consisting of Na andK), and 2 to 6% of sodium sulfate, said percentage of NaOH being basedon the total weight of the /constituents, said detergent comprising0.25% to before reaching an excessive height, then repeating suchwithdrawal and return of a portion of said solution, and permitting thecontents of said residual material in said solutionto increase to anamount substantially greater than that originally present therein.

3. The method of washing beverage containers and the like in whichresidual material from the group consisting of metal salts of shortchain fatty acids, proteins and carbohydrates are present as foamingagents, comprising the steps of contacting the said containers with anaqueous solution of the detergent composition comprising at least 85%alkali metal hydroxide, 3 to 11% water soluble alkali metal silicate, asrepresented by the formula XMezQYSiO: (Me representing a memberof thegroup consisting of Na and K) and 2-6% alkali metal sulfate, the totalweight I of these three last mentioned compoundsrepresenting 0.25% to10%-of the weight of the aqueous solution, said solution havingincorporated therein entrained gases normally causing generation offoam, which is rapidly dissipated because of this detergent;

4. The method of washing beverage containers and the like in whichresidual material from the group consisting of metal salts of shortchain fatty acids, proteins and carbohydrates are present as foamingagents, comprising the steps of contacting said containers with anaqueous solu- 10% of the weight of the solution.

8. A foam-dissipating solutionv for washing beverage containers and thelike containing mostly water, from a mere trace up to- 1% proteinaceousmaterial, a detergent comprising at least 85% of sodium hydroxide, 3 to11% of a water-soluble sodium silicate as represented by the formulaxmzoysioz, and 2 to 6% of sodium sulfate, the percentage of saiddetergent components being based on their total weight, these threecomponents representing 0.25% to 5 10% of the weight of the solution.

' 9.- A foam-suppressing detergent for washing beverage containers andthe like, comprising by weight approximately 90.7% of sodium hydroxide,approximately 5.3% anhydrous sodium metasilicate and approximately 4% ofsodium sulphate.

' 10. A foam-suppressing detergent for washing beverage containers andthe like, comprising by weight approximately 92.6% of sodium hydroxide,approximately 3.4% of anhydrous watera glass and approximately 4% ofsodium sulphate.

11. -A foam-suppressing detergent for washing beverage containers andthe like, comprising by weight approximately 93.4% of sodium hydroxide,approximately 2.6% of silica reacted with said sodium hydroxide andapproximately 4% of sodium sulphate.

EUGENE F. HILL

